beginner's guide to oc

8/3/2019 Beginner's Guide to OC

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Beginner's guide to overclocking

Tutorial: Get more speed from your processor for free

Processors News

By Adam Oxford and Neil Mohr

Squeeze a bit more juice from your stock CPU settings with this handy guide to overclocking

Back in the days when the average desktop PC was barely capable of running anything more demanding

than a word processor, overclocking your CPU to get 1,000 performance from a 300 chip was almost

as big a necessity as switching off the 'turbo' button to underclock and run non speed-limited software.

The world has changed. A modern multi-core CPU has a much longer shelf life than its ancestors, since

performance today is as much a factor of the number of cores and microcode as it is raw clockspeed. An

Intel Q6600 bought four years ago is unlikely to feel sluggish whatever the situation, and upgrading isn't

expensive anyway.

For the reasonable outlay of 150, you can pick up anything from the latest Sandy Bridge chips through

to an excessively powerful sixcore processor from AMD. The basics, though, remain the same: why buy

a new chip when you can save money by overclocking the one you have?

The techniques used in CPU overclocking are largely unchanged since those early days: simply ask your

processor's clock to run a little faster, do something to take care of the extra heat produced, and you're

done.

It's true that most CPU architectures have a cap beyond which they simply won't perform, but the good

news is that up to 5GHz is possible for new Intel processors, and you won't need any flashy coolants to

make it happen. We'll talk a lot about clocks in this article, so here's a definition.

Your CPU's clock speed is calculated by taking the base clock (a signal supplied by the clock generator

on the motherboard) and then applying a multiplier. On newer motherboards, the base clock will be

133MHz by default, whereas for Core 2 or older CPUs, the base clock varies between 100MHz and

166MHz.

The important thing to remember is that the CPU speed is always defined by this external influence from

the motherboard. It doesn't just run; it needs to be told how.


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Sometimes this is easy. If you own an Extreme Edition chip, one of the new K-series models, or any

unlocked Intel CPU, then you'll be able to select the multiplier. So a Core i7 980X running at 3.33GHz

(133MHz base clock, x25 multiplier) can be overclocked to 4GHz just by increasing the multiplier to 30.

If you don't have an unlocked chip the multiplier will be fixed at a set value or, in the case of the Core i7

and i5 CPUs we've seen, you'll be given a restricted set of options in the BIOS to set the multiplier or

apply a very small overclock.

Base clock

If you can't increase the multiplier, you'll need to increase the base clock itself, and that's where your

choice of motherboard is all-important - better boards give you more options.

A warning though: the base clock affects the other buses in your machine. This includes the PCI-e bus

used by your graphics card, so either your GPU needs to be well cooled, or you'll need to be able to

'decouple' the CPU and GPU in the BIOS and leave your graphics card running at stock speed.

The other stalwart of overclocking is the CPU voltage setting - as you increase the processor speed, it's

necessary to increase the voltage supplied to the processor in order to retain stability. This isn't a blunt

instrument - increase the voltage too much and you'll actually introduce more instability.

Increased voltage also leads to greatly increased core temperatures, as we'll see later on.

Hardware choices

Are you thinking of building a system just for overclocking? We used an MSI P55-GD65 for our Intel-

based tests. This is a solid board that costs less than 100 yet still offers a wide range of all-important

BIOS settings.

In case you aren't confident with fiddling around too deeply in the BIOS, it also has broad options that

increase clockspeeds across the board, and can automatically find a modest but stable overclock.

As far as the chip goes, any one of Intel's Core 2, Core i5 or Core i7 processors is a great place to start.

We think the best choice right now is the Core i5 2500K, a 3.33GHz chip that will hit 4GHz reasonably

easily. That processor leaves you a little scuppered when it comes to motherboards though - the Z68

chipset is yet to mature, so we're still looking for the perfect partner for this chip.


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The first important step here is to reduce the memory bus speed to the lowest setting - ideally 400MHz

with basic latencies of 8-8-8-8-24. These will help eliminate memory-based errors, so you can be more

certain that the processor has caused a lockup by throwing a wobbly.

Then it's time to turn things up a little. Increasing the base clock by 10MHz at a time is safe, but also

incredibly boring. We prefer jumping in with both feet and assuming a free 10 per cent increase is a safe

bet.

With the 3.2GHz Phenom II 955, that means an initial overclock to 3.5GHz or a Front Side Bus speed of

219GHz. This worked fine, so we started pushing a little harder. Eventually we hit 3,728MHz with the

FSB at 233MHz before the Cinebench X264 benchmark fell over, though Windows itself remained

stable.

We cranked the FSB back down, and eventually settled on 228MHz and 3,648MHz as being stable.

Of course, the Black Edition has its multiplier unlocked. This enables increases in the CPU speed without

altering the system bus from its stock speed, which is better for everyone. We returned to the unstable

level of 3,700MHz, using a 200MHz FSB and a multiplier of 18.5x and increased the voltage by a single

step from the stock 1.350v until the system was stable again.

Then we returned to slowly increasing processor speed via the FSB until it became unstable again. In the

end, we managed to achieve a maximum stable overclock of 3,904MHz with a 1.56v core voltage. That's

a 205MHz FSB, 19x multiplier and a worryingly elevated core temperature of 60.5C!

We did find this a little unstable though, so we went back a couple of steps to our best solid results:

3,838MHz with a 19x multiplier and a 202MHz FSB.

Overclocking step-by-step

1. Use quality components


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A decent motherboard and RAM are the foundations of easy overclocking. Without access to the right

settings, there's little chance of getting a decent overclock going. Without access to the right kit, you

won't get the settings. Ironically, you might need to upgrade before proceeding.

2. Keep everything cool

A heavy-duty cooler offers quieter running than stock coolers. One with a sturdy heatpiped copper base

and 120mm fan is going to provide more efficient cooling than the standard block type. You can

overclock on the stock cooler, of course, but we probably wouldn't.

3. Apply thermal paste


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Remember, a good application of thermal paste is essential to help your cooling efforts. We've found that

we get the best results by applying an tiny amount initially, spreading this around with the heatsink itself,then removing and cleaning the majority from just the cooler.

4. Consider water-cooling

You could, if you're looking to take your processor a long way, treat yourself to water-cooling likeCoolIT's ECO ALC. These modern self-contained units are easy to use, run quieter than a lot of fans, and

are covered by some all-encompassing warranties for peace of mind.

5. Grab some benchmarks


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Seeing the difference is pretty important; you'll want to get hold of something you can run before and

after overclocking. Many people use games like Far Cry 2 and Crysis, which include built-in

benchmarks, or you could try Cinebench x264, a dedicated benchmark tool.

6. Get official tools

Intel's Desktop Control Center and AMD Overdrive are essential if you want to gain access to all your

processor's features, although these will only really work with super high-end chips. You'll be stuck with

the BIOS otherwise.

The dirty work: Ready to take your processor up a notch? It's easy

1. Master the BIOS


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The preferred way to overclock your processor is to use the BIOS. The best overclocking boards provide

a dedicated section to adjust the settings for the memory, processor and system bus, along with automaticsettings, preset options and recovery.

2. Bench then run

Run your benchmarks to get the base numbers for your PC. Once done, reboot and hit [Delete] to enter

the BIOS. The MSI P55-GD6 lists its main tweaking options in the Cell menu - 'Adjust CPU base

frequency', 'Adjust CPU ratio' and 'CPU voltage' are the main ones.

3. Multiplier boost


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The Core i7 870 CPU Ratio can be raised from 22 to 24, so that's an easy place to start. Save the changes

and exit the BIOS, and then see if you can boot into Windows at the higher clockspeeds. If that appears

to be working fine, reboot and go back into the BIOS.

4. Base clock kick

Raise the CPU Base Frequency by 10MHz, save the changes and boot Windows to check for stability. If

all is fine, return to the BIOS to repeat the process until you can no longer boot. Try increasing the CPU

Voltage by 0.1V and test to see if this improves things.

5. Voltage tweak


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If you're still facing problems, either increase the voltage a bit more, or try dropping the multiplier and

increasing the base clock to go faster. You may need several attempts to balance the three settings. Intelchips are fairly robust, but watch your voltage.

6. Go third party

Most motherboard manufacturers provide their own overclocking utilities. The ASUS effort offers up a

decent automatic mode, although it does err on the side of caution a little too much. In this instance it

stopped at 1.4v, with a maximum CPU speed of 3.4GHz.

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